(1) Field of the Invention
The present invention relates to an apparatus and method for bending and forming sheet material such as sheet metal. In particular, the present invention relates to an apparatus and method of bending and forming opposite ends of sheet metal to form a U-shaped channel member, by employing rollers that roll over and form the channel bends without leaving tool marks in the sheet metal.
(2) Description of the Related Art
There are many different types of apparatus and various different methods that have been employed in forming channel bends in sheet metal to produce U-shaped channel members from the sheet metal. Examples of prior art apparatus and methods of forming sheet metal are disclosed in U.S. Pats. No. 4,002,049 and 4,434,644. In one example of a prior art sheet metal forming apparatus, bends in sheet metal are formed by an operating head having a cylindrical shape with a V-shaped notch extending longitudinally across the peripheral surface of the head. The V-shaped notch is defined by opposed side wall surfaces extending into the notch. The intersection of one of the wall surfaces and the peripheral edge of the head forms a fixing edge of the head, and the intersection of the other of the wall surfaces and the peripheral surface of the head forms a bending edge.
The cylindrical tool head is received in a semicircular groove formed in a tool holder of the prior art apparatus. The cylindrical tool head is positioned in the tool holder groove with the V-shaped notch formed in the tool head exposed. The tool head is secured in the holder groove for rotation of the tool head relative to the holder.
In operation of these prior art bending apparatus, the cylindrical tool head and holder are lowered toward an edge of a sheet metal blank supported on a die plate. The spaced edges of the tool notch engage a surface of the sheet metal adjacent to an end of the sheet metal to be formed in a channel bend. As the tool and holder are continued to be lowered they exert a force on the sheet metal end and bend the sheet metal end over the edge of the die plate positioned below the sheet metal. As the sheet metal end is bent over the die plate, one edge of the V-shaped notch engages a top surface of the sheet metal and holds the sheet metal down against the die plate while the other edge of the V-shaped notch bends the end of the sheet metal over the end of the die plate. As the other edge of the V-shaped notch bends the end of the sheet metal over the die plate, it slides in friction engagement over the end of the sheet metal. The sliding friction engagement of the tool notch edge over the sheet metal end often produces undesirable tooling marks in the sheet metal surface.
In various different types of prior art sheet metal forming apparatus similar to the prior art apparatus described above, the bends formed in sheet metal are produced by the sliding engagement of a tool over a surface of the sheet metal. In these other types of metal forming processes, as the bend in the sheet metal is formed by the tool the tool also produces undesirable tooling marks in the surface of the sheet metal due to the sliding engagement of the tool over the sheet metal. In many situations the presence of the tooling marks in the surfaces of the finished sheet metal products is unacceptable and additional finishing operations must be performed on the sheet metal products to remove the tooling marks. These additional finishing operations increase the expense involved in forming sheet metal products.
In prior art methods of forming U-shaped channel members from sheet metal stock, the channel members are often formed by first producing one channel bend along one side of the sheet metal, and then forming the second channel bend along the opposite side of the sheet metal. This prior art method of forming channel members often results in one of the channel bends having dimensions different from the other channel bend, or one of the channel bends having an angular orientation that is different from the other channel bend.
What is needed to overcome the above described disadvantages of prior art sheet metal forming apparatus and methods is an apparatus and method for forming bends in sheet metal without marring or producing tooling marks in the surfaces of the sheet metal. What is also needed to overcome the above described disadvantages in forming channel bends in U-shaped channel members is an apparatus and method of forming the channel bends that produces equal angular orientations in each of the channel bends and equal dimensions of each of the channel bends formed.